1. Field of the Invention
This invention relates to a hot water extraction process for removing bitumen oils from tar-sands ore and more particularly to a process combining solvent and hot water extraction with air exclusion. The tar-sands ore is conditioned in hot water and then extracted with a water immiscible hydrocarbon solvent to form a mixture which settles into several phases. Each of these phases is thereafter processed to produce product bitumen oils and recycled process components.
2. Description of the Prior Art
A wide range of processes have been proposed for the extraction of bitumen from the surface-mined tar-sands ore. Of chief importance in developing and implementing a technique is the commercial viability and the ecological compatibility of the technique. Extraction techniques may be broken down into two major categories, those which employ water, either hot or cold, to float the bitumen oils away from the tar-sands, and those which employ an organic solvent to dissolve the bitumen oils. The processes utilizing water often involve air floatation, and often require addition of an alkaline material The water processes are not efficient, particularly on the lower bitumen content ore due to the formation of stable emulsions containing fine tar-sands ore particles, water and bitumen oils. The treatment of emulsions of large volumes of water containing bitumen oils and fine tar-sands ore particles has proven to be difficult.
Solvent processes without water are under development and typically follow the practices of the oil seed extraction technologies. Percolation and immersion-type extractors have been used, but the special designs and scale-up for abrasive tar-sands processing may be difficult. The solvent to bitumen ratio to be used for efficient extraction is often high, up to ten to one, which indicates high capital and utilities cost for the distillation recovery of the solvent. Spent sands have to be stripped of residual solvent, which is capital and energy intensive, before disposal for economic solvent usage. Existing methods using solvents to dissolve the bitumen oils from tar-sands, for example, as disclosed in U.S. Pat. No. 4,160,718, issued to Rendall, typically exhibit environmentally unacceptable losses of solvent, and have problems associated with hazards posed by the storage of large solvent inventories and require large quantities of water. Other solvent or hot water extraction processes or combinations are disclosed in U.S. Pat. Nos. 4,347,118, issued to Funk, et al. and 3,925,189, issued to Wicks, III. All of these methods, however, suffer commercial or ecological drawbacks, rendering them undesirable. A method for solvent and hot water extraction of bitumen from tar-sands is the subject of U.S. Pat. No. 4,424,112, issued to Rendall. This process however, requires numerous pieces of specialized equipment and is not highly energy efficient. The process is also adapted for a particular type of tar-sands found at Santa Rosa, N.M.